Shrinkable film forming copolyamides prepared by copolymerizing omegaaminoundecanoic acid and the salt of a dicar boxylic acid and trimethylhexamethylene diamine

ABSTRACT

SHRINKABLE FILM-FORMING COPOLYAMIDES WHICH ARE GLASSCLEAR IN APPEARANCE AND WHICH ARE OBTAINED BY POLYCONDENSATION OF 65-85% BY WEIGHT OF W-AMINO-UNDECANOIC ACID AND 35-15% BY WEIGHT OF A SALT OF A DICARBOXYLIC ACID AND A DIAMINE, BETWEEN 50 AND 100 MOL PERCENT OF THE DIAMINE BEING TRIMETHYLHEXAMETHYLENE DIAMINE, AND FILMS PRODUCED THEREFROM.

United States Patent Office 3,759,877 Patented Sept. 18, 1973 SHRINKABLE FILM FORMING COPOLYAMIDES PREPARED BY COPOLYMERIZING w-AMINOUN- DECANOIC ACID AND THE SALT OF A DICAR- BOXYLIC ACID AND TRIMETHYLHEXAMETH- YLENE DIAMINE Helmut Huhn and Lutz Hoppe, Walsrode, Germany, as-

signors to Wollf & Co. Aktiengesellsehaft, Walsrode, Germany No Drawing. Continuation-impart of application Ser. No. 88,123, Nov. 9, 1970, now Patent No. 3,692,748, which is a continuation of abandoned application Ser. No. 823,939, May 12, 1969. This application Feb. 24, 1972, Ser. No. 229,185 I Claims priority, application Germany, May 14, 1968, P 17 70 406.2 The portion of the term of the patent subsequent to Sept. 19, 1989, has been disclaimed Int. Cl. (308g 20/04 US. Cl. 260--78 A 2 Claims ABSTRACT OF THE DISCLOSURE Shrinkable film-forming copolyamides which are glassclear in appearance and which are obtained by polycondensation of 65-85% by Weight of w-amino-undecanoic acid and 35-15% by weight of a salt of a dicarboxylic acid and a diamine, between 50 and 100 mol percent of the diamine being trimethylhexamethylene diamine, and films produced therefrom.

This application is a continuation-in-part of application Ser. No. 88,123, filed Nov. 9, 1970, now US. Pat. 3,692,- 748, which in turn is a continuation of application Ser. No. 823,939, filed May 12, 1969, now abandoned.

This invention relates to shrinkable film-forming copolyamides which are glass-clear in appearance, and to a process for their production.

In addition to the known production of clear polyamides from terephthalic acid and trimethyl hexamethylene diamine (US. patent specification No. 3,150,117), it is also known that two or more starting monomers can be polycondensed to form copolyamides. For example, adipic acid and terephthalic acid can be polycondensed with isophorone diamine (see Chemische Industrie 4, 7 (1966)). Another process for the production of transparent copolyamides is known from DAS 1,265,412 according to which mixture consisting of a dicarboxylic acid, 3-amino-methyl-3,5,5-trimethyl cyclohexylamine and amino caproic acid and/ or ll-arnino-undecanoic acid or their lactams is polycondensed.

Unfortunately, all the aforementioned polyamides and copolyamides are either totally unshrinkable or can only be shrunk at elevated temperatures. In some cases, considerable shrinkable stressed occur at temperatures as low as 20 to 50 C. Shrink films produced from copolyamides of their kind are unsuitable for the shrink-wrapping of products that are particularly sensitive to temperature. In addition, expensive plant, for example in the form of shrinkable tunnels producing air heated to at least 150 C. are required to initiate the shrinkage process.

It is an object of this invention to provide a shrinkable film-forming clear copolyamide whose shrinkage and stressing on shrinkage are substantially nil up to a temperatnre of 40 C. and which, at a temperature of 75 C. for example, has a high shrinkage capacity hitherto unattained with conventional polyamides and copolyamides despite the fact that it only undergoes average stressing on shrinkage.

This object is accomplished by a shrinkable film-forming transparent copolyamide consisting essentially of 65- 85% by weight of recurring structural units of the formula tNH-(CH CO-} and 35-15% by weight of recurring structural units of the general formula wherein Y is and R is a member selected from the group consisting of (a) a mixture in any proportions of the two isomers and mixtures in any proportions thereof, n is a number between four and eleven, m is a number between two and eleven,

between 50 and 100 mol percent of the radical R being selected from the group consisting of the mixture in any proportions of the two isomers said copolyamides having a relative solution viscosity (as measured on a solution of 1 g. of polymer in 100 ml. of 96% H 50 at 25 C.) in the range of from 1,6 to 2,6.

Copolyamides of this kind are completely dimensionally stable and undergo hardly any stressing during shrinkage at a temperature below 40 C., whilst the stressing on shrinkage of conventional copolyamides at this temperature is as high as from 0.5 to 0.88 kp./mm. At the same time, the shrinkage capacity of the copolyamides according to the invention at C. is from 7 to 8 times greater than that of conventional polyamides and copolyamides. As a result, it is possible to wrap temperaturesensitive products with extreme care in shrink film and, at the same time, to obtain a considerably higher throughput heretofore, using conventional shrink-packing Inachinery, such as shrinkage tunnels, because the amount of energy expended per shrink pack can be considerably reduced. Furthermore, the product to be packed can be held very firmly in place as required, by virtue of the high shrinkage capacity of the packaging film coupled with its favourable shrinkage stressing.

Since the copolyamides according to the invention are insoluble in methanol, they may' readily be used as a packaging material for methanol-containing feedstock or as a substrate for forming laminates from plastics materials dissolved in methanol, unlike other copolyamides, for example those polycondensed from amino-undecanoic acid according to DAS 1,265,412.

The copolyamides according to the invention are obtained by a process for the production of a shrinkable film forming transparent copolyamide which comprises copolycondensing 65-85% by weight of w-amino undecanoic acid and 35-15% by weight of a salt of a dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid, and an acid of the general formula wherein n is a number between four and eleven, with a diamine of the general formula H N--R-NH wherein R is (a) a mixture in any proportions of the two isomers H3 cm -CH1 CHz-CH3 CH3 H --CHz-CHz-NH2 The process is carried out in known manner at temperatures from 200 to 320 C., preferably from 270 to 290 C. The process and product are successful in attaining improved shrinkage properties according to the above stated conditions as disclosed in parent application Ser. No. 88,123 filed by us on Nov. 9, 1970. However, it is also possible by ensuring the absence of vacuum during reaction to also obtain considerable improvement in the stressing on shrinkage properties; that is the relative high values reported in Examples 1-3 are an improvement over the results occurring if vacuum is used during reaction. In the case of Example 2, such values in -kp./mm. are 0 at 40 C., 0.61 at 75 C. and 0.54 at 90 C. where the melt of reactants is heated under vacuum.

It is also of advantage to add acetic acid and phosphoric acid to the aforementioned mixture of starting monomers, because it is possible in this way not only to promote polycondensation but also to homogenise the chain lengths of the macromolecules.

Measurements carried out on filaments of the coplyamides according to the invention stretched under heat in order to determine the degree of stressing to which they are subjected during shrinkage, have surprisingly shown that the filaments undergo hardly any stressing on shrinkage at temperatures down to freezing point, whilst the extent to which they are stressed during shrinkage actually reaches a maximum at 85 C. By contrast, the conventional nylon 11, tested under the same conditions underwent considerable stressing at temperatures of only C., the stressing increasing almost linearly with increasing temperature, up to a maximum at 90 C.

Shrinkage of the copolyamides according to the invention only begins at 50 C., rising sharply to a maximum at C. By contrast, the shrinkage of nylon 11, as a comparison material, increases only slowly with increasing temperature.

The production and properties of the copolyamides according to the invention are illustrated in, but are by no means limited by, the following examples and a table in which the results of comparative measurements on commercial polyamides are also set out.

EXAMPLE 1 2000 g. of amino-undecanoic acid adn 500 g. of the salt of terephthalic acid and a 25.075.0 mol percent mixture of the isomers 2,2,4- and 2,4,4-trimethylhexamethylenediamine are heated to 250 C. in an autoclave in the presence of 2.96 ml. of 2-normal acetic acid and 0.3 ml. of 3-normal phosphoric acid. Before heating, the contents of the autoclave are covered with oxygen-free nitrogen. The excess gas pressure which builds up is vented and the reaction components are polycondensed for 5 hours at 280 to 290 C. The product formed, is extruded under nitrogen pressure through a nozzle to form a filament which is granulated. The product is highly transparent, glossy and insoluble in methanol. It is impossible over a period of 5 hours to extract any monomeric components from the polymers by means of methanol and/ or water. The melting range is from 154 to 160 C., and the relative viscosity is 2.25 (as measured in the form of a solution of 1 g. in ml. of 96% by weight sulphuric acid).

The granulate can be blown in known manner into a tubular film by means of an extruder.

EXAMPLE 2 1620 g. of amino-undecanoic acid and 695 g. of the salt of terephthalic acid and a 5050 mole percent mixture of the isomers 2,2,4- and 2,4,4-trimethylhexamethylenediamine are polycondensed in an autoclave in the presence of 2.96 ml. of 2-normal acetic acid and 0.3 ml. of 3-normal phosphoric acid as described in Example 1. It is impossible over a period of 5 hours to extract any monomeric or polymeric components from the polycondensation products by means of methanol and/or water. The melting range of the polycondensate according to the invention is from 143 to 150 C. and its relative viscosity is 1.97 (as measured in the form of a solution of 1 g. in 100 ml. of 96% by weight sulphuric acid).

The granulate can be blown in known manner into a tubular film by means of an extruder.

EXAMPLE 3 To a suspension consisting of 1000 ml. of water and 193.3 g. of terephthalic acid are added 208.7 g. of a 75.0- 25.0 mol percent mixture of the isomers 2,2,4- and 2,4,4- trimethylhexamethylenediamine. The suspension is heated and stirred until a clear solution is obtained. Then 1600 g. (80% by weight) of aminoundecanoic acid, 53.5 ml. of 2-normal acetic acid, and 1 ml. of B-normal phosphoric acid are added. Before heating, the content of the autoclave is covered with oxygen-free nitrogen. The reaction mixture is kept at a temperature of 200-210 C. for one hour and the excess gas pressure which builds up is vented within one further hour, and then the reaction components are polycondensed for 6 hours at 280-290 C., while a slow stream of oxygen-free nitrogen is passing through the autoclave. The product formed is extruded under nitrogen pressure through a nozzle to form a filament which is granulated. Within 5 hours 0.5% of monomeric components are extracted by water. The melting range is from -l53 C., and the relative viscosity is 1.74.

The granulate can be blown in known manner into a tubular film by means of an extruder.

The shrinkage characteristics of the copolyamides according to the invention obtained in accordance with Examples 1, 2 and 3 and the corresponding data of commercial polyamides are set out in the following table.

The stressing and shrinkage data given in the table clearly demonstrate the distinct superiority of the copolyamides according to the invention to the commercial comparison products. They exhibit an extremely high shrinkage capacity at comparatively low temperatures without any deterioration in their dimensional stability up to a temperature of 40 C.; whilst conventional polyamides show a shrinkage at 75 C. which is from 8 to 20 times less than that of the products according to the invention.

The unexpected technological advantages of the products according to the invention are manifested, above all, in the limited amount of energy required to initiate shrinkage, in the nondamaging shrink packaging of temperature-sensitive products, in the higher throughput rate attributable to the smaller amount of energy required to the initiate shrinkage, and finally in the improvement in both the forming and the Welding properties attributable to the melting temperature which is reduced by some 50 to 80 C. At the same time, the copolyamides according to the invention are glass-clear in appearance and are insoluble in methanol, so that they are also eminently suitable for use in the packaging of methanol-containing feedstock, or as substrate films for the production of laminates by coating with solutions of plastics materials dissolved in methanol.

What is claimed is:

1. A process for the production of a shrinkable filmforming transparent copolyamide which comprises copolycondensing 65-85% by weight of w-amino undecanoic acid and 35-15% by weight of a salt of a dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid, and an acid of the general formula wherein n is a number between four and eleven, with a diamine of the general formula wherein R is (a) a mixture in any proportions of the two isomers CH CH; CH,-- CH 3CI-I -CH CH: LII

and

CH3 CH -CH, CH -C H -CI-I;

H CH: 2)m

or a mixture in any proportions of these radicals, wherein m is a number between two and eleven, and wherein between and mol percent of said diamine consists of the mixture in any proportion of the two isomers said process being carried out at temperatures from 200 to 320 C. in the absence of vacuum. 2. The product produced by the process of claim 1.

References Cited UNITED STATES PATENTS 3,627,736 12/1971 Raum et al 26078 HOWARD E. SCI-IAIN, Primary Examiner US. Cl. X.R.

Patent No.

UNl'l'l'll) SlA'll'lo' lA'l'l'lN'l OFFICE CEK'IUJICAIE Ub CORRECTION September 18, 1973 3 759 ,877 Dated Inventor) Helmut Huhn et 1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 20 formula (d) should read Column 2, line 35 in the formula, "CH

should read Column 4, line 1]., "adn" should read -and--.

Column 5, line 1, "Table 6" should read -Table UNl'll'll) S'lA'llfiS PATENT OFFICE L ClilillFlCA'lE Uh LJURRECTION lat m; N 3,759,877 Dated September 18, 1973 l Inventor) Ilelmut IIuhn et a Page 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, Claim 1, line 26 in the formula,

' "CH ll should read Signed and Scaled this eighteenth Day of November 1975 [SEAL] Arlesl:

RUTH C. MASON C. MARSHALL DANN Allmllng Ujjivvr ('nmmisszum'r n! Iulenrs and Trademarks 

